Method and apparatus for removing printing ink from paper



S. D. WELLS Filed Sept. 6, 1932 ATTORNEY;

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METHOD AND APPARATUS FOR REMOVING PRINTING INK FROM PAPER Patented June 12, 1934 UNITED STATES PATENT OFFICE METHOD AND APPARATUS FOR REMOVING PRINTING INK FROM PAPER Sidney D. Wells, Appleton, Wis., assignor to Lewis L. Alsted, Appleton, Wis.

18 Claims.

of Appleton, Wisconsin, the assignee of this ap-- plication.

Certain sources of supply of. old paper stock such as newspapers, directories and particularly telephone directories, books, catalogues and the like, become after {a certain length of time obsolete and are replaced by current issues, so that such material may be conveniently collected 20 to provide an available source of supply of stock for repulping into paper. However, even where such material is printed with a special type of ink, readily converted into colorless substances or substances corresponding in color to that of pulped, and as heretofore treated, so retards the passage of water or other fluid through it as to present a serious and diificult problem insofar as removal of the ink or other undesirable matter is concerned. i v

One of the objects of the present invention is to provide "a; method of and an apparatus for removing. ,pr" tin ink-and other impurities or esjiraile 1mm old paper stock which and with economies consistent with the requirements of actual commercial activity, and which so conditions and treats the stock as to subject all of the fibersthereof to the action of the deinking and cleansing medium in an eflicient and effective manner whereby to completely de-ink the old stock and convert it into a pulp possessed of all of the desirable characteristics of unused pulp and suitable for manufacture into paper having the color, texture, strength and otherdesirable qualities which the paper of the old stock originally possessed.

Broadley, the present invention consists in first beating the old paper stock under such conditions and to such extent as to nodulize the stock, that is, to work the same up into small pellets of uniform size, with each pellet containing a relatively great amount of water and a small amount of fiber. A batch of such nodulized stock is then subjected to the action of a the original color of the pulp, the stock, when @susceptibleaotracticeon a commercial scale de-inking and cleansing medium in such manner that the de-inking medium permeates all of the fibers of of diffusion to ink and other impurities and carry them off in solution with the de-inking medium. A washing medium is then employed and also exerts its action under the influence of difiusion and as a result the pellets, after such treatment, are free of ink or other impurities and consists entirely of fiber and water, the latter being slightly acidulated, if desired. 3

An important feature of the invention resides in effecting the de-inking or cleansing by diffusion. This is especially advantageous with the nodulized stock since the de-inking, by sulphurous acid, for example, is effected without breaking down the nodules, whereby any tendency of the fibers to mat and retard the cleansing or de-inking action is precluded. Furthermore, with a difiusion treatment, the stock retains its nodulized characteristics throughout the various stages of a multistage treatment and during its final washing.

More specifically, the present invention contemplates the reduction of the waste paper to nodules or pellets in a rod mill, or in a pulper or kneader, or in a combination of a beater and dewatering device (such as a screw press). The nodulized stock is then transferred to difiusers, preferably in the form of closed tanks, wherein the nodules are subjected to'the action of sulphur dioxide which isconverted into sulphurous acid the pellets under the influence when diifused through'and2-cOmbined with the a so I water in the nodules. In lieu of'the'use of sulphur dioxide 2, solution of sulphurous acid may be employed and preferably the treatment is carried out by using alternately weak and strong solutions of sulphurous acid. Sulphurousacid is desirable since it also acts as a reducing agent to discharge the ink and render it soluble in the dilute acid. Where inks are encountered which are soluble in an acid without necessitating any reduction, acids other than sulphurous acid may be employed, for example, sulphuric acid. However, since sulphurous acid combines acidity with reducing properties, it is usually preferable. The acid utilized is caused to travel through the diffusers and during its passage, is diffused throughout the nodules, to discharge the ink and dissolve it and thereby carry it on in solution. Following this treatment water is passed through the diffusers to effect appropriate washing and removal of sulphurous acid. In some instances, in order to stabilize the results obtained and counteract dissolve the ingredients of the any conflicting tendencies or deleterious effects that may arise from local water conditions or for other reasons it may be desirable to use water acidulated with sulphuric acid or some other equivalent strong acidulating agent. After such treatment the nodules are transferred to a stuff chest wherein the stirring action of the agitators readily resolve the nodules into a pulp possessing the appearance and the characteristics of unused pulp appropriate for manufacture into paper.

In the drawing;

The figure is a diagrammatic representation of one type of apparatus appropriate for carrying out the method of the present invention.

As shown in the drawing, the old paper stock is fed in any suitable way, as by means of a conveyor 1, into a rod mill designated generally at 2 which is of conventional construction in that it has the ordinary drum 3 rotated by power driven gearing 4 and containing a number of loose rods (not shown) extending longitudinally thereof and parallel to each other in the usual manner. For a full disclosure of such a rod mill, reference is made to my application for Apparatus and method of removing printing ink from paper, filed June 29, 1932, Serial No. 619,983. In the rod mill the old stock is subjected to the beating and rubbing action of the rods which disintegrates the paper and reduces it to fibers, without, however, injuring the fibers. As this beating and rubbing action is carried on in a water solution at relatively high consistencies, nodulization of the paper stock is effected, that is to say, with a small amount of water, the rubbing action on the stock is such as to work the fibers and the other ingredients of the disintegrated stock into pellets or nodules of uniform size and of high moisture content. The nodules so formed are substantially one-sixteenth to one-eighth inch diameter and possess a freeness on the Canadian freeness tester of from 600 to Z as compared to a freeness of 140 possessed by similar stock pulped in the ordinary way. The consistencies which may be advantageously employed range from approximately 12% to about 33%. The consistency usually employed is in the neighborhood of twenty five per cent, that is, three parts of water to one part of fiber.

The nodulized stock is transferred from the rod mill to one or more diffusers of which two, designated at 5 and 6, are illustrated. For the purpose of simplicity in illustration, the transferring is shown as being effected through a pipe 7 leading into the diffuser 6 and having a branch 8 leading into the diffuser 5. Gates or valves 10 and 11 are provided to regulate or shut off the flow through the pipes 7 and 8 and a suitably operated screw conveyor 13 may be provided for advancing the nodules through a portion at least of the pipe 8.

The diffusers are of similar construction and each includes a closed tank 15, each tank having a cylindrical body portion provided with a closed top 16 and a closed bottom 17. Within each tank a perforated false bottom 18 and a perforated false top 19 is provided, the false bottom 18 and the false top 19 being spaced from the bottom 1'7 and the top 19, respectively. The pipes 7 and 8 lead through the tops 16 and also through a suitable opening provided in the false top 19 so as to discharge into the space between the false bottom and top of each tank. At a convenient point, a storage tank 20 for sulphur dioxide is provided and connects by means of a pipe 21 and branches 22 and 23 with the tanks 5 and 6. respectively. A valve 24 is provided in the pipe line 21 and similar valves 25 and 26 are provided in the branches 22 and 23 whereby the supply of gas from the tank 20 may be shut off adjacent the tank or may be shut off adjacent either diffuser. The valves 24, 25 and 26 may be manipulated to supply sulphur dioxide to either or both diffusers. More than two diffusers may be employed, if desired.

Tanks 30 and 31 are provided for containing sulphurous acid gas, the tank 30 for strong solution of sulphurous acid and the tank 31 for a weaker solution. The bottoms of the tanks 30 and 31 are connected by valve controlled pipes 32 and 33 to a pipe line 34 leading to a pump 35 which delivers to a pipe line 36 having valve control branches 3'? and 38 leading into the diffusers 5 and 6. The pipes which supply sulphur dioxide or sulphurous acid to the diffusers lead through the bottoms thereof so that they discharge into the space between the bottom 1'7 and the false bottom 18 of each diffuser. The upper ends of the tanks connect with branches 40 and 41 equipped with valves 42 and 43 and communicating with a return pipe line 44 having valve control branches 45 and 46 which lead into the tanks 30 and 31, respectively. The pipe line 44 is extended, as indicated at 47, to a point of suitable discharge or to suitable recovery apparatus (not shown), and its communication with the discharge or recovery apparatus connection is controlled by a valve 49. The recovery apparatus may consist of a suitable combination of heat interchanger and evaporator effective to recover sulphur dioxide from the used acid solution and, if desired, of suitable means for facilitating recovery of the ink by coagulation and filtration.

The diifuser tanks 5 and 6 are provided with suitable valve controlled outlet connections designated at 50 and 51 and with suitable manhole openings 52 and 53. The outlet connections 50 and 51 discharge into a stuff chest 55 provided with a stirrer or agitator designated at 56.

In the rod mill the paper stock is completely defibered and the ink and other impurities loosened and the stock is worked up into pellets or nodules containing a relatively large amount of water, for example, from about six times to three times the weight of water to the weight of pulp. This, however, may vary and where, under the necessity of considerable handling, there is the requirement that the nodule characteristics be retained, the water content usually should be kept within four times that of the fiber, that is, 20% pulp to moisture.

The nodules are then transferred to the diffusers 5 and 6 where both diffusers are used and in the first instances the valves 24, 25 and 26 are open so that sulphur dioxide is admitted to the interior of the diffusers and combines with the water in the nodules to form sulphurous acid. After this treatment the valves 24, 25 and 26 are closed and the valve controlled branch 32 from the strong liquor tank 30 is opened so that strong liquor or a strong solution of sulphurous acid may be pumped by the pump 35 through the pipe line 36 and through the valve control branches 37 and 38 thereof into the lower ends of the diffusers. This strong solution of sulphurous acid is usually derived, in actual practice, from the leaching of a previous batch and consists of a solution of sulphurous acid with some ink dissolved therein. The approximate concentration of this strong solution is about 1.8% sulphur dioxide. As the strong solution travels up through the diffuser it is diffused through the nodules and therein it takes more ink and its concentration tends to vary, it becoming stronger at the bottom of the diffuser where the nodules are more strongly impregnated with sulphurous acid and weaker at the top where the nodules contain less sulphurous acid. As the treatment goes on, however, this variation becomes less and less and a uniform concentration and impregnation occurs. The liquid during its passage through the diffuser surrounds the nodules and is immediately absorbed therein due to their capillary attraction. In this way any substances in the ink capable of reduction are reduced; the ingredients of the ink are rendered soluble; and the sulphurous acid provides a solvent for such ink ingredients.

Depending upon its condition, which is observed or tested when leaving the diffusers, the strong liquor is either carried back to the strong liquor tank, or ,the weak liquor tank, or else is carried to a point of discharge or to suitable apparatus for recovering the sulphur dioxide and ink therefrom.

When the concentration in the diffuser is entirely uniform the supply of strong liquor is cut off and weak liquor is supplied to the diffuser or diffusers from the weak liquor tank 31 by closing the valve 32 and opening the valve 33. The weak liquor may have a concentration of .5% sulphur dioxide. The weak liquor is put through the diffusers, for the purpose of picking up all of the sulphurous acid that can be received from the nodules and depending on its condition is carried back from the diffusers to the strong liquor tank 30 or weak liquor tank 31 for reuse or else is taken to the recovery apparatus when the sulphur dioxide and also the ink, if desired,

is reclaimed. Dissolved ingredients of the ink or other dissolved impurities are, of course, carried off with the weak liquor.

sufficiently fast to preclude any material downward diffusion, thatis, dilution of the zone above by the zone below.v Thedepth of zone, however, should be great enough so that by the time a def inite zone has passed any strata complete equalization (of strength or concentration) of the liquor around and in the nodules has taken place;

' or, in the washingfloperation, effective washing consummated.

By having the final washing carried out with acidulated water-{any traces of the ingredients of the ink remaining in the fibers are converted to chemically stable compounds and in general the results obtained are stabilized and any deleterious effects arising from the use of the water employed or otherwise are counteracted.

After the nodulized stock has been treated in the manner described in the diffusers 5 and 6, the

outlets 50 and 51 are open and the stock dumped or flushed into the stuff chest 55. If desired, a hose may be inserted through the manholes 52 and 53 and utilized to flush out the treated stock. In the stuff chest the nodulized stock is broken up or resolved into pulp and may be readily manufactured into paper.

It is to be understood that the present invention, in its broader aspects, is not limited to a deinkable ink of any particular composition or to any specific de-inking medium. The main ad- It is also understood that .the process can be applied to the removal from. paper of coloring matter, which is dischargeable or solublein suitable solution of acids, alkalis or salts, or in water alone.

The apparatus and method specifically described have been selected for purposes of illustration and example and various changes in form, sequence, reagents, and proportions, as well as various omissions or additions may be resorted to without departing from the spirit of the invention or the scope of the subjoined claims.

The invention claimed is:

1. The herein described method of de-i nking printed paper which comprises nodulizing the paper, subjecting the nodulized stock to an upwardly traveling bath of de-inking fluid so that the de-inking fluid permeates the nodulized stock by difiusion to discharge the ink therefrom and then subjecting the stock to a diffusion washing to remove the de-inking fluid with the ink ingredients from the stock.

2. The herein described method of de-inking printed paper which comprises nodulizing the paper, subjecting the nodulized stock to an upwardly traveling bath of de-inking fluid so that the de-inking fluid permeates the nodulized stock by diffusion.

3. The herein described method of de-inking printed paper which comprises nodulizing the paper, subjecting the nodulized stock to a diffusion treatment with a fluid de-inking medium.

4. The herein described method of de-inking printed paper which comprises nodulizing the paper, subjecting the nodulized stock to a diffusion treatment with sulphurous acid.

5. The herein described method of removing printing ink from paper which comprises subjecting the paper to a beating and rubbing action in water and at a high consistency until the paper is reduced to fibers and worked up into nodules having a high, water content, and then subjecting the nodulized stock to a diffusion treatment with sulphur dioxide whereby sulphurous acid is formed in the nodules to provide a reducing agent and a solvent for the ingredients of the ink.

6. The herein described method of removing printing ink from paper which comprises subjecting the paper to a beating and rubbing action in water and at a high consistency until the paper is reduced to fibers and worked up into nodules having a high water content, and then subjecting the nodulized stock to a diffusion treatment with sulphurous acid.

7. Th e herein described method of removing printing ink from paper which comprises subjecting the paper to a beating and rubbing action in water and at a high consistency until the paper is reduced to fibers and worked up into nodules having a high water content, then subjecting the nodulized stock to a diffusion treatment with sulphur dioxide whereby sulphurous acid is formed in the nodules to provide a reducing agent and a solvent for the ingredients of the ink, and then subjecting the stock to a diffusion washing.

8. The herein described method of removing printing ink from paper which comprises subjectlng the paperto a beating and rubbing action in water and at a high consistency until the paper is reduced to fibers and worked up into nodules having a high water content, then subjecting the nodulized stock to a diffusion treatment with sulphur dioxide whereby sulphurous acid is formed in the nodules to provide a reducing agent and a solvent for theingredients of the ink, and then subjecting the stock to a diffusion washing with acidulated water.

9. The herein described method of reclaiming old paper stock which comprises nodulizing the stock and thereafter subjecting it to a diffusion treatment with a cleansing fluid.

10. The herein described method of reclaiming old paper stock which comprises nodulizing the stock and subjecting the nodulized stock to a diffusion treatment with sulphurous acid.

11. The herein described method of reclaiming old paper stock which comprises beating the stock in the presence of water and at high consistencies until the stock is reduced to fibers and worked up into pellets and thereafter subjecting the stock to a diffusion treatment with a fluid ink removing medium.

12. The herein described method of reclaiming old paper stock containing mechanical ground wood pulp which comprises beating the stock in a solution at high consistencies and until the stock is nodulized and thereafter subjecting the stock to a diffusion treatment with sulphurous acid and finally to a washing operation with acidulated water. I

13. The herein described method of reclaiming old paper stock containing mechanical ground wood pulp which comprises beating the stock in a solution at high consistencies and until the stock is nodulized and thereafter subjecting the stock to a diffusion treatment with sulphurous acid.

14. An apparatus for de-inking paper comprising means for disintegrating the paper into fibers in a water solution and nodulizing the fibers, a

diffuser for receiving and containing the nodulized stock, and a circulation system for subjecting the nodulized stock in the diffuser to an upwardly traveling bath of sulphurous acid whereby the sulphurous acid permeates the nodules by diffusion and thereby discharges the ink therefrom.

15. An apparatus for de-inking paper, comprising means for disintegrating the paper into fibers in a water solution and nodulizing the fibers, a diffuser for receiving and containing the nodulized stock, and a circulation system includin tanks containing strong and weak solutions of sulphurous acid, valve controlled supply and return connections between said tanks and said difiuser and a pump in said supply connection whereby the nodulized stock in the diffuser may be subjected to successive baths with strong and weak sulphurous acid in such -manrier that the said permeates the nodules by diffusion and thereby discharges the ink therefrom.

16. An apparatus for de-inking paper comprising means for disintegrating the paper into fibers in a water solution and nodulizing the fibers, a diffuser for receiving and containing the nodulized stock, and a circulation system including tanks containing strong and weak solutions of sulphurous acid, valve controlled supply and return connections between said tanks and said diffuser and a pump in said supply connection whereby the nodulized stock in the diifuser may be subjected to successive baths with strong and weak sulphurous acid in such manner that the acid permeates the nodules by diffusion and thereby discharges the ink therefrom, and means combined with said circulation system for subjecting the nodules in the diffuser to a final washing by diffusion.

17. An apparatus for de-inking paper, comprising means for disintegrating the paper into fibers in a water solution and nodulizing the fibers, a diffuser for receiving and containing the nodulized stock, a circulation system for subjecting the nodulized stock in the diifuser to an upwardly traveling bath of sulphurous acid whereby the sulphurous acid permeates the nodules-by diffusion and thereby discharge the ink therefrom, and means coordinated in its action with said circulation system for subjecting the nodulized stock in the diffuser to a diffusion treatment with sulphur dioxide, when desired.

18. An apparatus for de-inking nodulized paper stock comprising a diffuser containing the nodulized stock, means for supplying a de-inking medium into the lower portion of the diffuser so that the de-inking mediumrises up through the nodulized stock in the diffuser and permeates the nodules therein during its upward travel by diffusion thereby dissolving and carrying off the ink from the stock, and means connected with the upper portion of the diffuser for carrying off the de-inking medium and the ink contained therein.

SIDNEY D. WELLS. 

